As used in this part:

  (a) “Dark sky preserve” means an area designated in section 75102.

  (b) “Fully shielded” means outdoor light fixtures shielded or constructed so that no light rays are emitted by the installed fixture at angles above 15 degrees below the horizontal plane and also constructed so that the filament or light source is not visible to the naked eye when viewed from a point higher than 15 degrees below the horizontal plane.